Air conditioning system for a motor home vehicle or the like

ABSTRACT

A method and assembly for air conditioning a motor home vehicle or the like employing a heat transfer medium and cooling both the front passenger area and the rear living area using a single compressor source. The assembly having a compressor driven either by the vehicle&#39;&#39;s engine or a compressor driven by an electric drive motor, a first and second condenser mounted on the roof of the vehicle, a first and second evaporator mounted to a first and second blower, the first evaporator and first blower mounted under the dash of the vehicle and the second evaporator and second blower mounted on the roof of the vehicle.

United States Patent [191 Dawkins [451 May 27, 1975 AIR CONDITIONINGSYSTEM FOR A MOTOR HOME VEHICLE OR THE LIKE [21] Appl. No.: 423,280

[56] References Cited UNITED STATES PATENTS 2,054,350 9/1936 Weiland62/244 2,513,679 7/1950 Ritter.... 62/239 2,784,568 3/1957 Schjolin62/239 2,869,333 l/1959 Hoiby 62/259 2,907,182 10/1959 Kuklinski 62/2363,218,821 11/1965 Spatt 62/244 3,315,488 4/1967 Lind 62/259 3,347,31010/1967 Lind 3,719,058 3/1973 Waygood 62/243 Primary ExaminerWilliam .1.Wye Attorney, Agent, or FirmDunlap & Codding [5 7 ABSTRACT A method andassembly for air conditioning a motor home vehicle or the like employinga heat transfer medium and cooling both the front passenger area and therear living area using a single compressor source. The assembly having acompressor driven either by the vehicles engine or a compressor drivenby an electric drive motor, a first and second condenser mounted on theroof of the vehicle, a first and second evaporator mounted to a firstand second blower, the first evaporator and first blower mounted underthe dash of the vehicle and the second evaporator and second blowermounted on the roof of the vehicle.

11 Claims, 4 Drawing Figures PATENTED m 2 7 ms SHEEY m mmwaiou mm mm AIRCONDITIONING SYSTEM FOR A MOTOR HOME VEHICLE OR THE LIKE BACKGROUND OFTHE INVENTION 1. Field of the Invention This invention relates generallyto an assembly and method for air conditioning a motor home vehicle orthe like and more particularly but not by way of limitation to thecooling of both the front passenger area and the rear living area usinga single compressor source and without the use of an automotivecondenser used in conjunction with the vehicles radiator system.

2. Description of the Prior Art Various methods and assemblies have beendeveloped to air condition motor home vehicles or the like. There aretwo principal refrigeration type air conditioning systems currentlyemployed in such vehicles. The first is an air conditioning system inwhich the compressor is driven by the vehicles engine. The second is aseparate system which is operable when the vehicle is parked and employsan electric motor-driven compressor, powered by an electric circuitsupplied by an auxiliary gas generator or by an outside a-c line voltagesource.

These two principal systems are not without problems. The airconditioning unit driven off the vehicle engine is normally sufficientto cool the front passenger area but is not large enough or does nothave the capacity to cool the rear living area. Therefore, when themotor home is being driven, the rear living area is not cooledsufficiently. Also because of the size and weight of the motor homevehicle and the large engine horse power required to drive the vehicle,the radiator system coupled with a conventional automotive condenser isoften not sufficient to prevent the engine from overheating.

Also when the vehicle is parked, the separate electric motor-drivencompressor system driven by an a-c line voltage source is designed tocool the rear living area and is not sufficient to cool the frontpassenger area. If there is no a-c line voltage available, the rearliving area is not cooled.

The present invention anticipates and eliminates the above problems byinstalling two over-sized condensers on the roof of the vehicle so thatthe heat transfer medium being compressed by the engine drivencompressor can be condensed by the over-sized condensers on top of theroof and conducted to the evaporators installed under the dash of thefront passenger area and installed in the rear living area, thus coolingboth areas sufficiently without overloading or overheating the vehicleengine. Because of the separate oversized condensers more efficient heattransfer mediums can be used and more particularly but not by way oflimitation refrigerants such as Freon 22 can be used which heretoforecould not be used efficiently in automotive air conditioningapplications. It should be mentioned that the term over-sized is used inreference to automotive condensers which normally have two rows ofcondenser coils while the oversized condensers have four rows ofcondenser coils. By going to oversize condensers an over-condensingeffect is created which keeps excessive head pressure down when usingrefrigerants such as Freon 22 which has a lower boiling point thanstandard refrigerants used with automotive equipment.

Also, if for some reason the engine driven compressor cannot be used andan auxiliary a-c line voltage gas generator is provided for on thevehicle, both the front passenger and rear living area can be cooledwhile the vehicle is being driven.

If there is no alternating current line voltage available when thevehicle is parked, the vehicle engine can be started and idled so thatthe rear living area can be air conditioned.

A further problem with separate air conditioning systems driven by anauxiliary gas generator or by an outside a-c line voltage source is thatthe a-c motor-driven compressor, condenser and evaporator are mountedtogether as a unit and normally positioned over a fresh air opening inthe roof of the motor home. This requires extra roof reinforcementaround the fresh air opening, the overall height is a disadvantagebecause the compressor is not recessed in the roof, and the compressorand condenser blowers cause excessive noise to the people in the rearliving area.

By the present invention, the condenser and compressor are separate fromthe evaporators. The roofmounted a-c motor-driven compressor and theheavy duty condensers are installed over a closet with the compressorbeing recessed in the closet with the advantage of the noise beingsuppressed in the closet. No additional reinforcement is required in theroof due to the reinforcement construction of the closet structure andthe air conditioning plumbing can be hidden in the closet. By recessingthe compressor in the closet the minimum overall height of the vehiclecan be maintained.

SUMMARY OF THE INVENTION The present invention relates to an assemblyand method for air conditioning motor home vehicles employing a heattransfer medium for cooling both the front passenger area and the rearliving area. The assembly being distinguished by having a toggle switchwhich electrically switches the system operated from a twelve voltbattery source with a compressor driven by the vehicles engine to an a-cline voltage source driving a volt electric motor driven compressor. Theassembly having oversized condensers mounted on the roof of the vehiclefor receiving the compressed heat transfer medium from either the enginedriven compressor or the a-c electric motor driven compressor andsupplying an evaporator mounted under the dash of the vehicle and anevaporator mounted on the roof of the vehicle.

It is therefore a general object of the present invention to provide anassembly that will simultaneously cool both the front passenger area andthe rear living area without using separate air conditioning systems.

A further object of the present invention is to provide a method forcooling both a front passenger area and a rear living area without usingseparate air conditioning systems.

A still further object of the present invention is to provide an airconditioning system in which the air conditioning compressor can bedriven either by the vehicles engine or by an a-c electric motor-drivencompressor.

Another object of the present invention is to eliminate the use of anautomotive condenser used in conjunction with the vehicles radiator.

. Other objects and advantages of the invention will be evident from thefollowing detailed description when read in conjunction with theaccompanying drawings which illustrate the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of theair conditioning assembly mounted on a motor home vehicle.

FIG. 2 is a perspective view of the roof mounted electric drive motorcompressor and condensers.

' FIG. 3 is a diagrammatic illustration of the air conditioningassembly.

FIG. 4 is an electrical wiring diagram of the air conditioning assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 of thedrawings the air conditioning assembly is generally designated by thereference numeral and is mounted on a motor home vehicle 12. FIG. 1 isshown to point out the various electrical and mechanical equipment inthe assembly 10 and its preferred location on vehicle 12 but the drawingdoes not show the equipment electrically or mechanically connected.

Shown on the vehicles dash 13 of the vehicle 12 is a toggle switch 14for switching the system from a 12 volt battery source 16 mountedproximate to the vehicles engine 18 to a 1 10 volt ac line voltagesource provided either by connecting an electrical outlet 20 to anoutside source or by connecting to a separately mounted gas drivengenerator 22. When the assembly 10 is driven by the 12 volt batterysource 16 the engine 18 drives an automotive compressor 24 whichcompresses a fluid heat transfer medium which is conducted to roofmounted over-sized condensers 26 and 28. The over-sized condensers 26and 28 having four rows of condenser coils for maximum condensing whenusing refrigerants having low boiling points. The condensers 26 and 28have air circulating blowers 30. From the condensers 26 and 28 the heattransfer medium is conducted to an evaporator 32 ventedly connected by asuitable duct to a blower 34 mounted under the vehicles dash l3 and anevaporator 36 ventedly connected by a suitable duct to a blower 38mounted on the vehicles roof 30. When the assembly 10 is connected tothe,110 volt a-c source, an electric motordriven compressor 42compresses the heat transfer medium which is conducted through thecondensers 26 and 28 and to the evaporators 32 and 36.

FIG. 2 is a perspective view of the roof mounted condensers 26 and 28with the electric motor driven compressor 42 recessed in the roof 40 toprovide a minimum clearance as to the overall height of the vehicle 12.Shown around the recess 44 are water baffles 46 to prevent water fromcollecting or running into the bottom of the recess 44. Air circulatingfans are positioned adjacent to the condensers 26 and 28 to aid indrawing air through the condensers. A tubing conduit opening 48 is shownfor receiving suction and discharge conduits to the condensers 26 and 28and the compressor 42.

In FIG. 3 a conduit piping diagram is shown of the air conditioningassembly 10. When the engine driven compressor 24 is in use it receivesgaseous heat transfer medium through suction port 50 from a firstsuction conduit means 52 and a second suction conduit means 54 via athird suction conduit means 56.

From compressor 24 the compressed gaseous heat transfer medium isconducted through discharge port 58 to a first discharge conduit means60. Attached to the conduit means 60 is a high pressure cut out switch62 (i.e.. for pressures greater than 400 psi) which is responsive to thepressure of the heat transfer medium and is electrically connected to aclutch assembly 64 which engages and disengages the compressor 24 fromthe engine 18.

The heat transfer medium now passes into inlet port 25 of condenser 26and inlet port 27 of condenser 28 where it is condensed and the liquidheat transfer medium is discharged through outlet ports 29 and 31 to afirst liquid conduit means 64 and a second liquid conduit means 66. Thefirst liquid conduit means 64 has a dryer 68 connected to it forabsorbing moisture in the heat transfer medium and a sight glass 70 fordetermining if the asssembly 10 has any air circulating through thesystem. Also, the second liquid conduit means 66 has a dryer 72connected to it.

The liquid heat transfer medium in the first liquid conduit means 64 isnow conducted through a first expansion valve 74 and expanded into theinlet port 76 of evaporator 32. As the heat transfer fluid is evaporatedin evaporator 32, blower 34 circulates air past the evaporator coils forcooling the front passenger area. The gaseous heat transfer medium isnow discharged through outlet port 78 into first suction conduit means52 to be returned to compressor 24 to be recycled.

The liquid heat transfer medium in the second liquid conduit means 66 isconducted through a second expansion valve 80 and expanded into inletport 82 of evaporator 36. As the heat transfer fluid is evaporated inevaporator 36, blower 38 circulates air past the evaporator coils forcooling the rear living area. The gaseous heat transfer medium is nowdischarged through outlet port 84 into the second suction conduit means54 to be returned to compressor 24 via the third suction conduit means56. It should be mentioned that first and second expansion valves 74 and80 can also be capillary tubes or the like for use in expanding the heattransfer fluid prior to entry into evaporators 32 and 36.

When the electric motor driven compressor 42 driven by electric motor 86having an electrical outlet 20 is used rather than the engine drivecompressor 24, the gaseous heat transfer medium is received throughsuction port 88 from the first suction conduit means 52 via the thirdsuction conduit means 56 and the second suction conduit means 54. Thesuction conduit means prior to entering the suction port 88 alsoincludes a low pressure cut out switch (i.e., pressure less than 30 psi)which is responsive to the pressure of the heat transfer medium and iselectrically connected to the electric motor 86 which is shut off at lowpressures thus rendering the compressor 42 inoperable.

From compressor 42 the compressed gaseous heat transfer medium isdischarged through outlet port 89 to a second discharge conduit means92. The heat transfer medium is received through the inlet ports 25 and27 of the condensers 26 and 28. The heat transfer medium is condensedand discharged to the first and second liquid conduit means 64 and 66.

The same circulation cycle as described above using the vehicle motordriven compressor 24 is now used with the heat transfer medium enteringthe first and second expansion valves 74 and 80 and then intoevaporators 32 and 36. The "gaseous heat transfer fluid is thendischarged. throughoutlet ports 78 and84 and into first suction conduitmeans 52 and third suction conduit means 56 and second suction conduitmeans 54 for return to the suction port 88 of the compressor FIG. 4 isan electrical wiring diagram of the air conditioning assembly 10. Toggleswitch 14 being connected to the l2volt dc battery source 16 which isinstalled in the vehicle 12 and a 12 volt ac source from a transformer100 which is connected to the electrical outlet 20. The outlet can beconnected to an outside source of 110 ac line voltage or the alternategas drive generator 22. i

When the toggle switch 14 is connected to either the 12 volt ac or 12volt dc source, current is supplied to drive the air circulating blowers30 mounted with the condensers 26 and 28. Current is supplied also tothe blower switch 102 connected to blower motor 104 which drives theblowers 34 vented to evaporator 32. Thermostat 106 is connected to theblower switch 102 to control the predetermined temperature of the frontpassenger area.

High pressure cut out switch 62 is also connected to the electriccircuit and signals the clutch 64 to disengage the.automotive compressor24 from the vehicle engine 18 should the heat transfer mediums pressureexceed 400 psi in the air conditioning assembly 10.

Also electrically controlled from the 12 volt toggle switch 14 is blowerswitch 108 and thermostat 110 which turns on and off blower motor 112driving blowers 38 vented to evaporator 36. Connected to this electricalcircuit is low pressure cut out switch 90 which through relay 114 turnselectrical motor 86 driving the compressor 42 off should the heattransfer medium pressure drop below 30 psi in the air conditioningassembly 10.

Electric motor 86 driving compressor 42; is.,connected through relay 114directly to the electrical outlet 20 for obtaining 110 a-c line voltagefrom an outside source or the alternate gas driven generator 22. Shownconnected to the outlet 20 is voltage indicator 2] which would warnagainst using the ac linesource should the voltage drop below 110 volts.

Changes may be made in the construction and arrangement of parts orelements of the various embodiments as disclosed herein withoutdeparting from the spirit and scope of the invention as defined in thefollowing claims.

What is claimed is:

l. A refrigeration typeair conditioning assembly employing a heattransfer medium for use in a motor home vehicle or the like having afront passenger area and a rear living area, and which is equipped withan engine, a source of d-c voltage, and an electrical outlet forconnecting the motor vehicle or the like to a source of a-c linevoltage, comprising: i i

a first compressor means, having a suction port and a discharge port.for compressing the gaseous heat transfcr medium passing therethrough;

means for drivingly connecting said first compressor to the engine ofthe vehicle;

a second compressor means having a suction port and a discharge port,for compressing the gaseous heat transfer medium passing therethrough;

an'ele'ctric drive motor drivinglyconnected to said second compressorm'ounted onthe vehicle;

electrical conductor meansconnectedto said electric drive motor forelectrically connecting said electric drive m'otorto the electricaloutlet-of the motor vehicle to provide a-c line voltage to said electricdrive motor; v a i a first condenser coil means, having an inlet portand an outlet port and mounted on the motor vehicle, for condensing thegaseous heat transfer medium passing:therethrough into the liquid state;

a second condenser coil means, having an inlet port and an outlet portand mounted on the motor vehicle, for condensing the gaseous heattransfer medium passing therethrough into the liquid state;

I a first evaporator coil means, having an inlet port and an outlet portand mounted on the motor vehicle proximate to the front passenger area,for evaporating the liquid heat transfer medium passing therethroughinto the gaseous state;

a second evaporator coil means, having an inlet port and an outlet portand mounted on the motor vehicle proximate to the rear living area, forevaporating the liquid heat transfer medium passing therethrough intothe gaseous state;

first discharge conduit means interconnecting the discharge port of saidfirst compressor means and the inlet ports of said first and secondcondensor coil means, for conducting gaseous heat transfer medium fromsaid first compressor means to said first and second condensor coilmeans;

second discharge conduit means interconnecting the discharge port ofsaid second compressor means and the inlet ports of said. first andsecond condensor coil means for conducting gaseous heat transfer mediumfrom said second compressor means to said first and second condensorcoil means;

first liquid conduit means interconnecting the outlet port of said firstcondensor coil means and the inlet port of said first evaporator coilmeans for conducting liquid heat transfer medium from said firstcondensor coil means to said first evaporator coil means;

second liquid conduit means interconnecting the outlet port of saidsecond condensor coil means and the inlet port of said second evaporatorcoil means for conducting liquid'heat transfer medium from said secondcondensor coil means to said second evaporator coil means;

first suction conduit means interconnecting the outlet port of saidfirst evaporator coil means and the suction port of said firstcompressor means for conducting gaseous heat transfer medium from saidfirst evaporator coil means to said first compressor means;

second suction conduit means interconnecting the outlet port of saidsecond evaporator coil means and the suction port of said secondcompressor means for conducting gaseous heat transfer medium from saidsecond evaporator coil means to said second compressor means;

third suction conduit means interconnecting the out let ports of saidfirst and second evaporator coil means;

first blower means disposed adjacent to said first evaporator coil meansfor moving air over said first evaporator coil means and into the frontpassenger area; and i second blower means disposed adjacent to saidfirst evaporator coil means for moving air over said second evaporatorcoil means and into the rear living area;

air circulating means mounted on the vehicle for moving air over saidfirst and second condensor coil means;

a first expansion valve means connected to said first liquid conduitmeans and disposed adjacent to the inlet port of said first evaporatorcoil means; and

a second expansion valve means connected to said second liquid conduitmeans and disposed adjacent to the inlet port of said second evaporatorcoil means.

2. The air conditioning assembly as defined in claim characterizedfurther to include:

means disposed in said first discharge conduit means and responsive tothe pressure of the heat transfer medium therein for disconnecting saidfirst compressor means from the engine when the heat transfer mediumpressure therein exceeds a predetermined value, whereby said firstcompressor means is rendered inoperative; and

means disposed in said second suction conduit means and responsive tothe pressure of the heat transfer medium therein for disconnecting saidsecond compressor means from said electric drive motor when the heattransfer medium pressure therein is less than a predetermined value,whereby said second compressor means is rendered inoperative.

3. The air conditioning assembly as defined in claim 1 furthercharacterized to include electrical switch means connected to the d-cvoltage source and to the a-c line voltage source so that the voltagesource to the means for drivingly connecting said first compressor meansto the engine can be switched to the electric drive motor drivinglyconnected to said second compressor means thereby switching the assemblyfrom said first compressor means to said second compressor means.

4. The air conditioning system as defined in claim 1 wherein said firstand second liquid conduit means are further characterized to include adryer for absorbing moisture from the heat transfer medium.

5. The air conditioning system as defined in claim 1 wherein said firstliquid conduit means is further characterized to include a sight glassfor determining whether there is air entrainment in the assembly.

6. The air conditioning system as defined in claim 1 wherein the conduitmeans are made of copper tubing and nylon hose for use with any type ofrefrigerant and more specifically Freon 22 as a heat transfer medium formaximum cooling efficiency.

7. The air conditioning system as defined in claim 1 wherein said firstcondenser coil means and said second condenser coil means are mounted onthe motor vehicle proximate to the rear living area.

8. The air conditioning system as defined in claim 7 wherein said firstcondenser coil means. said second condenser coil means, said secondcompressor means, said electric drive motor, and said air circulatingmeans are mounted together as a unit proximate to the rear living area.

9. The air conditioning system as defined in claim 8 wherein secondcompressor means is mounted in a recess in the roof of the vehicle sothat a minimum clear ance as to the overall height of the vehicle ismaintained.

10. A method for air conditioning a motor home vchicle or the likeemploying a heat transfer medium and cooling a front passenger area anda rear living area using a first compressor driven by the vehicle'sengine and a second compressor driven by an electric drive motor, afirst condenser coil and second condenser coil mounted on the roof ofthe vehicle, a first evaporator coil and second evaporator coil, 21first expansion valve and a second expansion valve mounted on the firstevaporator coil and second evaporator coil, respectively, the firstevaporator coil and a first blower being mounted under the dash of thevehicle, the second evaporator coil and a second blower being mounted onthe roof of the vehicle, comprising the steps of:

compressing gaseous heat transfer medium with the first compressor in adriven condition of the first compressor;

compressing the gaseous heat transfer medium with the second compressorin a driven condition of the second compressor; driving one of the firstand the second compressors via driving the first compressor via thevehicle engine in one condition and driving the second compressor via anelectric motor drive in one other condition; conducting the compressedgaseous heat transfer medium to the first and second condensor coils;

condensing the compressed gaseous heat transfer medium to a liquid heattransfer medium in the condensor coils; conducting the condensed liquidheat transfer medium to the first and second evaporator coils;

expanding the liquid heat transfer medium through the first and secondexpansion valves prior to the liquid heat transfer medium entering thefirst and second evaporator;

evaporating the liquid heat transfer medium to a gaseous heat transfermedium by circulation through the evaporator coils;

circulating air using the first and second blowers past the evaporatorcoils to cool the passenger area and the rear living area; and

returning the gaseous heat transfer medium from the evaporator coils tothe compressor.

11. The method as defined in claim 10 further characterized, after thestep of condensing the compressed gaseous heat transfer medium to aliquid heat transfer medium in the condenser coils, to include the stepof: passing air over the first and second condenser coils to aid thecondenser coils in condensing the compressed gaseous heat transfermedium.

1. A refrigeration type air conditioning assembly employing a heattransfer medium for use in a motor home vehicle or the like having afront passenger area and a rear living area, and which is equipped withan engine, a source of d-c voltage, and an electrical outlet forconnecting the motor vehicle or the like to a source of a-c linevoltage, comprising: a first compressor means, having a suction port anda discharge port, for compressing the gaseous heat transfer mediumpassing therethrough; means for drivingly connecting said firstcompressor to the engine of the vehicle; a second compressor meanshaving a suction port and a discharge port, for compressing the gaseousheat transfer medium passing therethrough; an electric drive motordrivingly connected to said second compressor and mounted on thevehicle; electrical conductor means connected to said electric drivemotor for electrically connecting said electric drive motor to theelectrical outlet of the motor vehicle to provide a-c line voltage tosaid electric drive motor; a first condenser coil means, having an inletport and an outlet port and mounted on the motor vehicle, for condensingthe gaseous heat transfer medium passing therethrough into the liquidstate; a second condenser coil means, having an inlet port and an outletport and mounted on the motor vehicle, for condensing the gaseous heattransfer medium passing therethrough into the liquid state; a firstevaporator coil means, having an inlet port and an outlet port andmounted on the motor vehicle proximate to the front passenger area, forevaporating the liquid heat transfer medium passing therethrough intothe gaseous state; a second evaporator coil means, having an inlet portand an outlet port and mounted on the motor vehicle proximate to therear living area, for evaporating the liquid heat transfer mediumpassing therethrough into the gaseous state; first discharge conduitmeans interconnecting the discharge port of said first compressor meansand the inlet ports of said first and second condensor coil means, forconducting gaseous heat transfer medium from said first compressor meansto said first and second condensor coil means; second discharge conduitmeans interconnecting the discharge port of said second compressor meansand the inlet ports of said first and second condensor coil means forconducting gaseous heat transfer medium from said second compressormeans to said first and second condensor coil means; first liquidconduit means interconnecting the outlet port of said first condensorcoil means and the inlet port of said first evaporator coil means forconducting liquid heat transfer medium from said first condensor coilmeans to said first evaporator coil means; second liquid conduit meansinterconnecting the outlet port of said second condensor coil means andthe inlet port of said second evaporator coil means for conductingliquid heat transfer medium from said second condensor coil means tosaid second evaporator coil means; first suction Conduit meansinterconnecting the outlet port of said first evaporator coil means andthe suction port of said first compressor means for conducting gaseousheat transfer medium from said first evaporator coil means to said firstcompressor means; second suction conduit means interconnecting theoutlet port of said second evaporator coil means and the suction port ofsaid second compressor means for conducting gaseous heat transfer mediumfrom said second evaporator coil means to said second compressor means;third suction conduit means interconnecting the outlet ports of saidfirst and second evaporator coil means; first blower means disposedadjacent to said first evaporator coil means for moving air over saidfirst evaporator coil means and into the front passenger area; andsecond blower means disposed adjacent to said first evaporator coilmeans for moving air over said second evaporator coil means and into therear living area; air circulating means mounted on the vehicle formoving air over said first and second condensor coil means; a firstexpansion valve means connected to said first liquid conduit means anddisposed adjacent to the inlet port of said first evaporator coil means;and a second expansion valve means connected to said second liquidconduit means and disposed adjacent to the inlet port of said secondevaporator coil means.
 2. The air conditioning assembly as defined inclaim 1 characterized further to include: means disposed in said firstdischarge conduit means and responsive to the pressure of the heattransfer medium therein for disconnecting said first compressor meansfrom the engine when the heat transfer medium pressure therein exceeds apredetermined value, whereby said first compressor means is renderedinoperative; and means disposed in said second suction conduit means andresponsive to the pressure of the heat transfer medium therein fordisconnecting said second compressor means from said electric drivemotor when the heat transfer medium pressure therein is less than apredetermined value, whereby said second compressor means is renderedinoperative.
 3. The air conditioning assembly as defined in claim 1further characterized to include electrical switch means connected tothe d-c voltage source and to the a-c line voltage source so that thevoltage source to the means for drivingly connecting said firstcompressor means to the engine can be switched to the electric drivemotor drivingly connected to said second compressor means therebyswitching the assembly from said first compressor means to said secondcompressor means.
 4. The air conditioning system as defined in claim 1wherein said first and second liquid conduit means are furthercharacterized to include a dryer for absorbing moisture from the heattransfer medium.
 5. The air conditioning system as defined in claim 1wherein said first liquid conduit means is further characterized toinclude a sight glass for determining whether there is air entrainmentin the assembly.
 6. The air conditioning system as defined in claim 1wherein the conduit means are made of copper tubing and nylon hose foruse with any type of refrigerant and more specifically Freon 22 as aheat transfer medium for maximum cooling efficiency.
 7. The airconditioning system as defined in claim 1 wherein said first condensercoil means and said second condenser coil means are mounted on the motorvehicle proximate to the rear living area.
 8. The air conditioningsystem as defined in claim 7 wherein said first condenser coil means,said second condenser coil means, said second compressor means, saidelectric drive motor, and said air circulating means are mountedtogether as a unit proximate to the rear living area.
 9. The airconditioning system as defined in claim 8 wherein second compressormeans is mounted in a recess in the roof of the vehicle so that aminimum clearance as to the overall height of the vehicle is maintained.10. A method for air conditioning a motor home vehicle or the likeemploying a heat transfer medium and cooling a front passenger area anda rear living area using a first compressor driven by the vehicle''sengine and a second compressor driven by an electric drive motor, afirst condenser coil and second condenser coil mounted on the roof ofthe vehicle, a first evaporator coil and second evaporator coil, a firstexpansion valve and a second expansion valve mounted on the firstevaporator coil and second evaporator coil, respectively, the firstevaporator coil and a first blower being mounted under the dash of thevehicle, the second evaporator coil and a second blower being mounted onthe roof of the vehicle, comprising the steps of: compressing gaseousheat transfer medium with the first compressor in a driven condition ofthe first compressor; compressing the gaseous heat transfer medium withthe second compressor in a driven condition of the second compressor;driving one of the first and the second compressors via driving thefirst compressor via the vehicle engine in one condition and driving thesecond compressor via an electric motor drive in one other condition;conducting the compressed gaseous heat transfer medium to the first andsecond condensor coils; condensing the compressed gaseous heat transfermedium to a liquid heat transfer medium in the condensor coils;conducting the condensed liquid heat transfer medium to the first andsecond evaporator coils; expanding the liquid heat transfer mediumthrough the first and second expansion valves prior to the liquid heattransfer medium entering the first and second evaporator; evaporatingthe liquid heat transfer medium to a gaseous heat transfer medium bycirculation through the evaporator coils; circulating air using thefirst and second blowers past the evaporator coils to cool the passengerarea and the rear living area; and returning the gaseous heat transfermedium from the evaporator coils to the compressor.
 11. The method asdefined in claim 10 further characterized, after the step of condensingthe compressed gaseous heat transfer medium to a liquid heat transfermedium in the condenser coils, to include the step of: passing air overthe first and second condenser coils to aid the condenser coils incondensing the compressed gaseous heat transfer medium.